If you cannot open an Excel file and see Excel cannot open the file because the file format or extension is not valid error, see this post.

If Microsoft Project cannot open a file, you can repair corrupted Microsoft Project files by following the solutions mentioned in this post.

In other words, you can retrieve an older version of a .docx file, but not a .jpg. I might add that if you use cloud-based applications to create and edit your files, these may also save versions.